The light shaping lens array of an image reader is comprised of a combination of prism lenses, cylindrical lenses and diffusers, which are used to shape and direct light onto a target. The lens array is positioned optically between the target and illumination light sources and embedded into the enclosure of the reader during the manufacturing stage and depending on the application, the array is adjusted in relation to the target and illumination light source and fixed in place. These applications vary with the type of symbology to be imaged and may include standard, high density or long range code reading.
This means that the image reader must be customized to provide different light shaping capabilities for each unique application. Further, depending on what application is needed and more specifically, what focal length is needed, the objective lens must be positioned over the image sensor and then fixed in place. Therefore, the adjustment of the light shaping lens array is in addition to the required adjustment of the objective lens.
U.S. Pat. No. 6,371,374 issued to Schwartz et al on Apr. 16, 2002, describes a manufacturing technique whereby the light shaping optical elements are adjusted until the desired distances from the illumination sources are obtained and then the elements are fixed in place. These adjustments are in addition to the adjustment of the objective lens in relation to the image sensor. The main drawback to this method therefore, is the need for numerous adjustments including to the light shaping optical elements and the objective lens.
U.S. Pat. No. 6,034,379 issued to Bunte et al on Mar. 7, 2000, describes a technique in which the illumination assembly of an image reader contains different types of illumination sources for different code reading applications. These sources are also replaceable. This technique would require that the illumination assembly be contained on its own circuit board, which would be removable from the image reader. While this technique does provide some flexibility in the amount of code reading applications the reader can be used with, it is an expensive and complex.
U.S. Pat. No. 6,601,768 issued to McCall et al on Aug. 5, 2003, discloses an optical plate of diffuser elements to diffuse light from the illumination assembly, which is snap-fitted into the frame of an image reader module. This invention however, does not disclose a technique whereby a different optical plate can by used for different code reading applications.
Therefore there is need for optical image readers capable of using various preassembled light shaping element arrays that meet the requirements of different applications